The molecular dynamics of polymers can be explained by means of systems constructed on the bases of springs and pistons. One of the most valid models is the Vangheluwe model and its parametric constants are determined by the graphic method1, the Marquardt iterative method, and the hyperplane method. Another important model is the Zurek model, whose parametric constants are determined using a graphic method and the iterative Marquardt method. In this paper, we apply the least squares technique to evaluate the numerical constants of both models. The least squares technique leads to a system of non-linear equations that were solved using the Newton-Raphson method. The results of both models were noticeably better than the available methods.